Step 1

Preheat the oven to 400 degrees F. Lightly grease a 9X13-inch baking pan (I use glass or ceramic). Alternately, you can use individual, large, oven-safe ramekin dishes (about 10 ounces, 4 1/2-inches or so).

Step 2

For the filling, in a 5- or 6-quart pot set over medium heat, add the olive oil, onions (or shallots), celery, carrots, potatoes, salt and pepper. Cook for 1-2 minutes, stirring often. Cover the pot with a lid, reduce heat to medium-low, and continue to cook, until the vegetables are lightly steamed and mostly tender (they'll cook a bit more later), 5-7 minutes. Check every couple of minutes to stir and make sure they aren't sticking. Add a couple tablespoons water or broth if the mixture is overly dry. Scrape the mixture to a plate or bowl.

Step 3

Return the pot to medium heat. Add the butter and cook until melted. Stir in the flour and whisk to combine. Continue cooking, stirring constantly, for 1-2 minutes as the flour/butter sizzles.

Step 4

Gradually whisk in the broth and milk, adding 1/2 to 3/4 cup at a time and incorporating it completely before adding more. Bring the mixture to a simmer, stirring constantly, and cook until the sauce has thickened, 5-7 minutes.

Step 5

Stir in the chicken, frozen peas, and reserved vegetables and remove from the heat. Season to taste with additional salt and pepper, as needed!

Step 6

Carefully ladle/pour the pot pie filling into the prepared baking dish(es). Let the mixture cool until warm (this helps not melt the butter in the pie crust/biscuits so they stay flaky and tender). If you can't possibly wait, it's ok, just hurry and top it with biscuits or pie crust and get it into the oven ASAP.

Step 7

If using a pie crust topping, roll out the pie crust to desired thickness to fit on top of the baking dish with about a 1/4-inch overhang. Roll/lift the pie crust to fit evenly over the top of the pot pie filling - make sure it's resting directly on the filling and not hanging above suspended on the edges of the pan. Trim the edges to about 1/4-inch (if needed). Flute the edges or tuck them into the inside of the baking dish.

Step 8

For a biscuit topping, make the biscuits by whisking together the flour, baking soda, baking powder, and salt. Cut in the butter until the butter pieces are about pea-size (or grate it in with the large holes of a box grater and toss with the flour). Add the buttermilk and mix quickly and gently until it forms a cohesive ball (don't overmix). Turn the mixture onto a lightly floured counter and press into a rough rectangle about 1/2-inch thick.

Step 9

Gently fold the dough in half or in thirds, repeating for a total of 4-5 times and pressing it gently into a 1/2- or 3/4-inch thick rectangle after the last fold. These folds, combined with the cold butter, are what help to create flaky layers in the biscuits.

Step 10

Cut the rectangle into about 15 equal pieces (square). Top the pot pie with the biscuits, evenly spaced apart.

Step 11

Bake the pot pie for 30-35 minutes until the pie crust or biscuits are golden and cooked through. Let the pot pie rest for 5-10 minutes out of the oven before serving.